We propose to develop a homogeneous, liposome-based immunoassay for antinuclear antibody (ANA) diseases. In the phase I studies, we will demonstrate the feasibility of the approach for only one ANA disease, i.e., the mixed connective tissue disease. The major nuclear antigen U1-RNP, for this autoimmune disease has been cloned in bacteria with a proprietary technology. We will incorporate the cloned U1-RNP into liposome membrane to prepare target-sensitive liposomes. Glucose-6-phosphate dehydrogenase will be entrapped as a reporter enzyme. A homogeneous, colorimetric, inhibition assay will be developed as a prototype for future diagnostic products which will include other ANA antibodies.